1. Field of the Invention
This invention relates to mercury manometers for a purge bubbler liquid level control system or the like. More particularly, this invention relates to mercury manometers comprising a mercury column with electrical contacts imbedded in the walls of the column for sensing specific liquid levels.
2. Description of the Background Art
Presently, there exist many types of instruments designed to maintain a predetermined level in a tank. One such type of instrument comprises a purge bubbler system in which compressed air is forced through a bubbler line to the liquid containing tank to bubble out of the line through the liquid contained in the tank. The resultant hydrostatic back pressure in the line is then sensed with a mercury manometer to control the fluid pumps or the like fluidly connected to the tank, thereby controlling the level of the liquid in the tank. Such purge bubbler systems are particularly suitable for use in the sanitation fields, such as sewage lift stations, because the flow of compressed air through the bubbler line constantly purges the line of contaminants while balancing the liquid head pressure in the tank.
Mercury manometers which are used in conjunction with purge bubbler systems as described above, typically comprise a mercury column having electrical contacts imbedded in the wall of the column for connection to the electrical controller of the purge bubbler system. A mercury reservoir is connected to the input of the mercury column for storage of a quantity of mercury at atmospheric or other calibrated pressure representative of zero (0) relative pressure. U.S. Pat. No. 3,947,692 discloses one such mercury manometer, the disclosure of which is hereby incorporated by reference herein.
An improved mercury manometer is disclosed in U.S. Pat. No. 4,297,081, the disclosure of which is also incorporated by reference herein. The mercury manometer disclosed in Patent '081 comprises a mercury manometer having a base plate composed of a transparent material and having the input and overflow reservoirs and the mercury column machined into the surface of the base plate. An O-ring is positioned within an O-ring groove about the periphery of the reservoirs and the mercury column. A transparent face plate is then bolted to the face of the base plate to produce the fluid-tight reservoirs and mercury column by the sealing action of the O-ring between the base plate and face plate. As disclosed, the base plate is machined to produce a mercury reservoir of sufficient volume to match the mercury column volume. Thus, the resolution of the rise of the mercury within the mercury column is a function of the cross-sectional area of the mercury column, with smaller cross-sectional area defining a longer length mercury column thereby providing greater resolution between electrical contacts. Conversely, larger cross-sectional area of the mercury column defines a shorter length mercury column with lower resolution due to the physical size of the electrical contacts used to make contact with the mercury column and the ability of the technician to visually determine small changes in movement of the mercury in the column. Indeed, as disclosed in U.S. Pat. No. '081, the resolution of the mercury manometer is limited to the diameter of the electrical contact screws. Thus, greater resolution can only be obtained by using smaller diameter contact screws or the like or staggering the contact screws across a wider mercury column. It is noted, however, that the greater width mercury column also decreases the visual resolution of the manometer when visually viewed by the technician via the transparent face plate.
Therefore, it is an object of this invention to provide an apparatus which overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which is a significant contribution to the advancement of the mercury manometer art.
Another object of this invention is to provide a mercury manometer having greater electrical resolution than prior art mercury manometers of a given overall size.
Another object of this invention is to provide a mercury manometer having increased visual resolution over prior art mercury manometers of a given overall size.
Another object of this invention is to provide a mercury manometer having a mercury column of small cross-sectional area and being positioned in an accordion shape having a reduced overall length but providing great resolution over that which is attainable by a non-accordion shaped mercury column.
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.